Many powered devices rely upon rectifiers to convert an alternating current (AC) power source to a direct current (DC) power source. In recent years, energy harvesting for low-power devices has emerged as a use for rectifiers. Devices such as implantable biomedical sensors, for example, can be powered by receiving radio frequency (RF) energy and rectifying the RF energy to provide a DC voltage to the sensor. Rectified RF energy can then be used in place of a battery, allowing the size of sensors to be reduced.
Increasing rectifier efficiency in such applications makes more power available for use by a sensor or allows a sensor to operate with less received RF energy. Conventional attempts at increasing rectifier efficiency, however, are limited to fixed operating conditions.